<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>边框外轮廓：outline</title>
    <style>
      .box {
        width: 400px;
        height: 400px;
        border: 1px solid black;
        margin: 0 auto;
        margin-top: 100px;
        /* outline-width: 10px;
        outline-color: blue;
        outline-style: dotted; */
        outline-offset: -100px;

        /* outline复合属性写法，outline-offset不是outline的子属性，不能写在一起 */
        outline: 10px blue dotted;
      }
    </style>
  </head>
  <body>
    <div class="box">边框外轮廓：outline</div>
    <div style="text-align: center">外轮廓不占位置</div>
  </body>
</html>
